| New energy resources are very important to human society’s sustainable development. In all of them, solar energy is one of most promising ones, because it is unpolluted and Infinite. Solar cell, which is also called photovoltaic, is one of most feasible methods to exploit solar energy, and it has been used in our daily life and production. Recently pgotovoltaic industry develops very rapidly, but its proportion in sum of world energy consumption is still low because the cost of fabricating soalr cells is too high.Now, crystalline silicon solar cells are dominant in photovoltaic industry, because they have very high photovoltaic conversion efficiency and high stability. To reduce the cost of solar cell, many researchers are focus on thin film solar cell materials; thin film solar components can save materials significantly compared with crystalline silicon solar cell. Among of all, sulfide compounds CuInS2 and SnS are considered promising ones. They are direct band gap materials and their absorbance coefficients both are about 105 cm-1, solar cell based on them can be made only several micrometers thick, save lots of materials. Their band gaps are matched with solar spectrum very well and the theoretical conversion efficiency are very high. Many vacuum methods are used to prepare them, but the fabrication processes of vacuum methods are complicated and cost too much. So many researchers are devoted to study non-vacuum methods to produce these films. Particles inks printable methods based on solution are considered promising ways, because they are very simple and have the potential to realize large-scale production.This paper demonstrated the preparation of photovoltaic absorbed thin films CuInS2, SnS and buffer layers In2S3 based on metal particles inks, which are prepared by reducing metal salt in poloys solution. We have studied the effect of heat treatment on the metal particles precursor films, especially in hydro sulfide atmosphere. Scanning electron microscopy, X-ray diffraction patterns, Raman shift, spectrum measurement and Hall Effect measurement and so on were adopted to analyse the prepared films. In summary, followed results are obtained:1. Large-size grains and compact CuInS2 films were prepared based on Cu -n particle inks assisted with air heat treatment. At first, Cu-In nanoparticles were reduced by NaBH4 solution in ploys. The sizes of Cu-In particles are about 100 nm averagely. Particles and a certain amount of Polyvinylpyrrolidone (PVP) were dissolved into ethanol to make inks. Cu-In precursor films were sulphurised in hydro sulphide atmosphere directly, but prepared CulnS:are very small sizes. Then we heated Cu-ln precursor films in air at 350℃to burn down organic and followed sulphuriesd in hydro sulphide, grain sizes of prepared CuInS:grew largely and compact films were prepared at 550℃.2. A small device was prepared by usual fabrication process based on prepared CuInS2 thin films. At first, dozen of nanometers CdS buffer layer was deposited on CuInS2 film by chemical bath. Second, widow layer intrinsic ZnO was prepared by magnetron sputter. Third, we sputtered ITO transparent conductive films as top electrodes; carbon paste was dropped on it as point electrode.0.5 cmx0.5 cm device was made and had an open voltage of 250 mV, its current is 0.2 mA.3. SnS thin films were prepared based on Sn nanoparticles inks. Sn nanoparticles were prepared by reducing metal salt in poloys. Dissolve Sn nanoparticles and appropriate amount of PVP into ethanol to make inks, then dropped onto silicon or glass substrate. SnS thin films were prepared in H2S at low temperatures of 180℃and 200℃. Their band gaps are between 1.29 eV to 1.31 eV, which match with solar spectrum very well and suitable as photovoltaic films. The grain sizes of prepared SnS films were very small, but large grains are necessary to fabricate high efficiency devices. We attempted to sulphurising Sn nanoparticles films at high temperatures, but SnS2 phase was found in prepared films, which can’t be photovoltaic films.4. ImS3 thin films were prepared based on In nanoparticles inks. In nanopartilces were prepared by reducing metal salt in poloys. Dissolved In nanoparticles and appropriate amount of PVP into ethanol to make inks, then dropped onto silicon or glass substrate. (3-ImS3 films were prepared by sulphurising In precursor films at 450℃and 500℃. Nono-rod grew in some places of prepared In2S3 films, which can decrease reflectance of surface of InS3films. Crystalline character of In2S3growth on CuInS? thin films was better than that on glass and silicon surface. The bad gap of prepared In2s3is about 2.29-2.38 eV, which is consistent with other researchers’study. |
